title: Inverse relationship between age-dependent erythrocyte activity of methaemoglobin reductase and prilocaine-induced methaemoglobinaemia during infancy.
abstract: We have measured plasma concentrations of local anaesthetics, and the substance fraction of methaemoglobin (MetHb), in infants less than 3 months of age, after application of a lignocaine-prilocaine cream (EMLA). A total of EMLA 2 g was applied over four different skin areas, totalling 16 cm2, for 4 h before anaesthesia for a minor surgical procedure. Sampling was carried out before and 4, 8 and 12 h after application. Maximum MetHb values (median = 2.24%) were obtained usually at 8 h and were significantly (P less than 0.001) higher than before application (median 1.32%). The plasma concentrations of local anaesthetics were low (maximum values: prilocaine 78 ng ml-1, lignocaine 412 ng ml-1). The activity of erythrocyte MetHb reductase (cytochrome b5 reductase) was analysed. Data from a previously studied group of infants aged 3-12 months were included also. Enzyme activity did not reach adult levels until after the age of 3 months. It showed a good inverse correlation with the maximum MetHb values after application of EMLA. Although the MetHb concentrations in the infants younger than 3 months were small, the enzyme capacity may be overloaded when EMLA is administered at the same time as other MetHb-inducing agents. It is concluded that the use of EMLA should be restricted in this age group.
authors.affiliation: Department of Anaesthesiology, University Hospital, Uppsala, Sweden.
authors.forename: A
authors.initials: A
authors.lastname: Nilsson
authors.forename: G
authors.initials: G
authors.lastname: Engberg
authors.forename: S
authors.initials: S
authors.lastname: Henneberg
authors.forename: K
authors.initials: K
authors.lastname: Danielson
authors.forename: C H
authors.initials: CH
authors.lastname: De Verdier
mesh_terms: D000367:Age Factors; D000779:Anesthetics, Local / Q000494:pharmacology*; D042966:Cytochrome-B(5) Reductase / Q000097:blood*; D004338:Drug Combinations / Q000494:pharmacology; D004912:Erythrocytes / Q000201:enzymology*; D005260:Female; D006801:Humans; D007223:Infant; D008012:Lidocaine / Q000097:blood / Q000494:pharmacology*; D000077442:Lidocaine, Prilocaine Drug Combination; D008297:Male; D008708:Methemoglobinemia / Q000139:chemically induced*; D009247:NADH, NADPH Oxidoreductases / Q000097:blood*; D011318:Prilocaine / Q000097:blood / Q000494:pharmacology*
chemical_list: D000779:Anesthetics, Local; D004338:Drug Combinations; D000077442:Lidocaine, Prilocaine Drug Combination; D011318:Prilocaine; D008012:Lidocaine; D009247:NADH, NADPH Oxidoreductases; D042966:Cytochrome-B(5) Reductase